I have a 2004 ford freestar. P0193 code. Replaced fuel filter and worked for.short time. Light back on. Runs fine for most part just stumbles on acceleration once or twice a tank of gas. Usually when it gets low. So regulator,fuel pump, sensor? I am not sure where to start.

As the Fuel Rail Pressure Sensor also operates using vacuum you can unplug the small vacuum line and use a handheld brake type vacuum pump. Just make sure to plug the line you removed.
I forget exactly the values you should see, but at the least you should see some changes when increasing or decreasing vacuum.

Have you ever changed the spark plugs? ..changed the fuel filter?.. air filter??.. replace these and see if it gets better.. you can do this yourself..
get one of these..
2004 Ford Explorer Repair Manual Vehicle Maintenance

http://www.rockauto.com/en/catalog/ford,2004,explorer,4.6l+v8,1427802,literature,repair+manual,10335

P0193 FORD - Fuel Rail Pressure Sensor Circuit High Input
Symptoms - Engine Light ON (or Service Engine Soon Warning Light)
- Engine will not start Possible causes - Excessive resistance in the circuit
- Low or no fuel
- Wiring harness connector of the fuel pressure sensor
- Fuel Rail Pressure Sensor
- Fuel Pump

Check the pressure regulater...Also make sure there is no kinks in the line..You really need to see a data stream instead of just codes..Alot of time people see a code and replace part you need to watch the pressures and see whats going on..Look make sure the vacuum line on the regulator is ok

You are describing low fuel pressure (fuel pump) problem. When you say you replaced the fuel filter, where did you find this filter on the 2004 Sonata? The problem, there is no Fuel Filter, per se, there is a 'SOCK' at the bottom of the fuel pump assembly which serves as a filter, inside the fuel tank. By the way, you mentioned the Check Engine Light came on. Did you scan for any codes in the computer (ECU)? If you did, what were the codes?

The check engine light will always come on when the engine stalls.It could be your fuel filter needs replaced or your fuel pump is going out. The fuel pumps can heat up and stop working, then after they have a chance to cool off they will work just fine until they get hot again.

Mine is on too (MIL, with p0193), 2005 freestar. My dealer can't figure it out for some reason? So I went out and bought a code reader, will fix it myself!
Anyways it can be the fuel pressure sensor (approx $100 for part), the fuel pump, or regulator on the fuel line, not too sure what they are worth, and time for labour? I am currently looking for a test gauge to check the pressure in the fuel line to see if it is pump or regulator or sensor. Hopefully your service guys can run a few similar tests and determine what needs to go.

most likely not the fuel filter- try plugs and wires... could be a number of things, if the vehicle runs fine while in park and doesnt hesitate, most likely is sprk plugs and wires or a transmission problem...

how to repair a Ford Freestar fuel rail pressure sensor

disconnect battery overnight. It will clear codes if you don't have the scan tool. It may run rough for a few miles while it relearns your car's routines.

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